Fluorinated ion exchange membranes are known in the art wherein the ion exchange polymer precursor contains pendant side chains in sulfonyl fluoride form. These groups are converted to ionic form such as by hydrolysis with an alkaline material or by treatment with ammonia. An example of such prior art teaching is disclosed in Connolly and Gresham U.S. Pat. No. 3,282,875.
Additionally, in the prior art is disclosed a technique of treating cation exchange polymers for modification of the property of relative cationic transport. This teaching is set forth in Mizutani et al. U.S. Pat. No. 3,647,086 in preparation of an ion exchange membrane wherein permeation selection of different classes of cations is improved. As set forth in this patent, a cation exchange polymer of a high molecular weight polymer contains chemically bonded acid amide groups. These groups are present at the substantial surface portion to satisfy the equation: EQU A/(A + B) .times. 100 = 15 - 10.sup.-.sup.5 %
wherein (per gram of dry membrane) A is the number of acid amide bonds and B is the number of cation exchange groups. The reaction is controlled such that the formation of the acid amide bonds takes place only at the surface or as set forth in the patent at the "substantial surface".